Ask any three people to define who they are talking about when they refer to “millennials,” and you’re apt to get at least four different answers. Generational boundaries are always somewhat blurry, but this generation seems particularly hard to pin down. Demographers usually define millennials as everyone born between the early 1980s and the late 1990s, or sometimes the early 2000s, but the lines are not hard and fast.

Meanwhile, the difference in life experience between a person born in 1982 and one born in 1998 is substantial: For one thing, the former remembers a time before the Internet, while the latter is a genuine digital native. For another, the older millennial was already in the workforce during the financial crisis of 2008, while the latter was still in grade school. Those are some of the key differences that lead Jesse Singal at Science of Us to wonder whether the millennials are not in fact two distinct generations, which he dubs Old Millennials and Young Millennials:

Old Millennials, as I’ll call them, who were born around 1988 or earlier (meaning they’re 29 and older today), really have lived substantively different lives than Young Millennials, who were born around 1989 or later, as a result of two epochal events that occurred around the time when members of the older group were mostly young adults and when members of the younger were mostly early adolescents: the financial crisis and smartphones’ profound takeover of society. And according to Jean Twenge, a social psychologist at San Diego State University and the author of Generation Me: Why Today’s Young Americans Are More Confident, Assertive, Entitled—and More Miserable Than Ever Before, there’s some early, emerging evidence that, in certain ways, these two groups act like different, self-contained generations.

Millennials are way less likely to follow “traditional” trajectories with regard to careers and marriage, both anecdotes and some data suggest. They often flit from job to job without staying in one place too long — they’re “The Job-Hopping Generation,” says Gallup — and are much more likely, relative to previous generations when they were in their 20s, to live at home and to put off family formation for a long time.

Again, this just doesn’t resonate, either for me or for most of my friends who are my age. We’re so normal! Yes, some of us have been hit harder than others by bad career luck or missteps, or by the massive national catastrophe of student debt, but for the most part we’ve had very “traditional” career paths.

This might explain why employers are so prone to making faulty assumptions about this generation—perhaps we are simply lumping them into a category that’s too broad to be descriptive. The differences Singal highlights also speak to the accelerating pace of change, especially changes in technology and the way we work. These changes are now happening so much more rapidly than ever before that the concept of generations may no longer be relevant or valuable to organizations. That’s especially true for millennials, who have been affected by these changes more strongly than their elders.

Consider that the typical organization has experienced five major organizational changes in the past three years, only one third of which have been successful, and a majority of leaders say changes need to happen even faster than they already are. Whereas someone entering the job market in 1975 may have encountered a workplace that looked familiar to someone who entered it in 1965, that’s much less true of 2015 and 2005. Organizations these days are undergoing multiple, sometimes radical changes every year, and in this environment of continual upheaval, the concept of generations may simply be a less meaningful guide for managing the workforce than it used to be, because members of a “generation” don’t have as much in common.